#include <iostream>

using namespace std;

int a = 5;
int main() {
    int a = 2;
    int c1 = a * 3;// 使用的是局部变量a
    int c2 = ::a * 3;// 使用的是全局变量a

    cout << "c1 = " << c1 << endl;
    cout << "c2 = " << c2 << endl;
    return 0;
}